Iron diffusion in a peraluminous sodium aluminosilicate melt at 0.1 MPA

Abstract

The chemical diffusivity of ferrous and ferric iron have been measured in a peraluminous sodium aluminosilicate melt over the temperature range 1250-1450°C by a diffusion couple technique. The diffusivity of ferrous iron defines an Arrhenius line with the equation: log10D = - 2.03±0 .09 -194300±58300/2 .303RT where the activat ion energy is -194.3±58.3 KJmo1-1. The diffusivity of ferric iron was estimated to be: log10D = -6.55±2.13 - 69700±16300/2.303RT where the activation energy is 69.7±16.3 KJmo1-1. The ferrous iron results are non-linear with respect to reciprocal temperature, and define a Fulcher equation of the form: log10D = - 7.16±.79 -280±4 3/ (T-1366) suggesting a decrease in activation energy of diffusion as temperature increases. This may be caused by a temperature induced disproportionation of the anionic melt structure. The diffusivity of ferrous iron increases sharply from 0 .1 MP a to 0.6 GPa suggesting a pressure induced depolymerization of the melt.